Manufacture of foamed copolyester thermoplastic elastomer sheet structures involves the addition of a foaming agent to thermoplastic copolyesters during melt-extrusion processes. The foaming agent may be a conventional chemical foaming agent, gas-encapsulating thermoplastic microspheres (e.g. Expancel® microspheres available from Eka Chemicals), or a combination thereof. The melt-extruded foam sheet structures find utility, among others, as vibration absorbing materials. Compression set resistance (ISO 1856, 22 hours, 70° C., 30% compression) of such sheet structures is typically 15-25%.
There remains a need for foamed copolyester sheet structures that have an enhanced compression set resistance (ISO 1856, 22 hours, 70° C., 30% compression) of less than 11%.